A high-profile Brooklyn murder trial was put on hold for a week until a new prosecutor could take over after the original prosecutor didn’t show up for court because of his alcoholism, a source with knowledge of the case told The Post.

Veteran Assistant District Attorney James Leeper went missing last Monday morning, just before closing arguments in the murder trial of Michael Magnan, who allegedly shot and killed a livery cab passenger during a robbery gone wrong in Flatlands in 2012.

Leeper has been suspended, a DA spokeswoman said.

The reason Leeper didn’t show up is because he is an alcoholic who relapsed and had to check into treatment, said the source.

Homicide chief Ken Taub came to court to explain the situation to Brooklyn Supreme Court Judge Albert Tomei and to say ADA Melissa Carvajal would give closing arguments — but that she would need a week to prepare by reading trial transcripts and court documents, the source said.

“ADA Leeper has been suspended pending a review,” a DA spokeswoman said Tuesday.

Leeper was the prosecutor who convicted Jonathan Fleming, a Brooklyn man who was exonerated and released last month after he spent 24 years behind bars because cops and prosecutors didn’t give his defense attorney a receipt that showed Fleming was on a Disneyland vacation in Florida when the murder happened.

After Fleming was released last month, his defense attorney Taylor Koss said he couldn’t accept that the missing receipt was a mistake.

“I know Jim very well. He was my direct supervisor for over a decade … My gut says he would never do this, but the reality of the situation is that he was there,” Koss said in April.

Tomei instructed the jury in the Magnan trial not to consider why there was a new prosecutor.